U.S. Pat. No. 5,253,585 discloses that a main charge of explosive is positioned symmetrically about a passageway-forming tubular member, such as a well pipe assembly. The charge is outwardly and radially spaced from the member and is coupled thereto by a dense medium, such as soil, which is adapted to transfer the produced explosive energy to the tubular member in the form of a pressure pulse applied by the medium. Initiation charges are supplied at the outer surface of the main charge, to initiate a detonation wave directed at the tubular member. A layer of dense medium is provided to confine the non-coupled surface of the charge and retard venting of explosive gases away from the tubular member. In the end result, concentrated, converging pressure pulses are applied to the tubular member on detonation, to cause it to be symmetrically crimped to restrict the passageway. U.S. Pat. No. 5,253,585 is herein incorporated by reference in its entirety.
U.S. Pat. No. 7,779,760 discloses a shaped charge assembly that comprises a housing, first shaped charge, a wave shaping relay charge and a second shaped charge located in the housing. The assembly is configured such that a first active element formed by initiation of the first shaped charge causes detonation of the wave shaping relay charge, which in turn causes initiation of the second shaped charge to form a second active element. The first active element moves beyond a second end of the housing to cause damage of a first kind to an external target and the second active element also moves beyond the second end to cause damage of a second kind to the target. Shaped charges are known in the art, and U.S. Pat. No. 7,779,760 is one example. U.S. Pat. No. 7,779,760 is herein incorporated by reference in its entirety.
There is a need in the art for one or more of the following:
Improved systems and methods for severing risers;
Improved systems and methods for remotely severing risers;
Improved systems and methods for remotely severing risers when the risers are risers connecting a floating vessel to a subsea wellhead